The present disclosure relates to light bulbs and in particular, to light bulbs comprised of light emitting diodes.
There are millions of light fixtures installed and being produced each year to provide both task and general lighting within schools, offices, homes, marine vessels, aircraft and the like. In recent decades, more and more of these applications have been addressed with the use of a fluorescent lamp as the light source. The advent of fluorescent lighting has been shown to be a significant improvement over incandescent light fixtures. Noted advantages are numerous and include a marked reduction in energy consumption for a given light output, reduced operating temperatures and a “cooler” light rendition index.
Fluorescent lamps are generally characterized as low-pressure arc discharge lamps. A conventional fluorescent lamp commonly used in troffer fixtures is shown in FIG. 1. The fluorescent lamp 10 includes an elongated envelope 12, whose internal wall is coated with a phosphor 14, and an electrode structure 16 at each end of the envelope. The envelope 10 also contains a quantity of an ionizable material 18, such as mercury, and a fill gas at low pressure. The fill gas can be, for example argon or krypton, or a mixture of these and other gases. Each electrode structure 16 includes a stem 20 having a tabulation 22 therein through which the envelope 10 is exhausted. Leads 24 and 26 are mounted on the stem 20 and pass through the stem for connection to terminals 28 and 30 disposed in an end cap 32. A cathode or filament-cathode 34 is connected across each pair of the leads 24 and 26. A voltage, usually supplied by a ballast transformer, is applied across the electrodes to ionize the ionizable material in the presence of the fill gas. The resultant ionization and recombination of ions and electrons produces radiation that interacts with the phosphor coating to produce visible light.
Fluorescent lamps of a given length and type generally do not vary greatly in the electrical power consumed. In the past, most attempts to change the power consumption have been in the direction of increasing the electrical energy requirements to produce a greater light output. However, due to the increasing cost of purchasing electrical energy, it is becoming increasingly desirable to reduce lighting loads in existing facilities. Various ways of doing this include the use of lower wattage light fixtures, the elimination of lamps from certain areas, and the reduction of the number of lamps used in a given area.
Although fluorescent lamps have numerous advantages relative to incandescent sources, these lamps still suffer from a number of disadvantages. For example, the ionizable material and fill gases used to generate the illumination pattern are relatively hazardous materials. Care must be taken to dispose of the fluorescent light fixtures to avoid releasing these materials into the environment. Moreover, fluorescent lamps require the use of a ballast transformer to cause the fluorescent lamps to illuminate. Ballasts frequently fail and require replacement. Moreover, as noted above, the energy costs for operating fluorescent lamps need further improvement.
Accordingly, there remains a need for improved light sources that maintain the advantages incurred with the use of fluorescent lamps yet overcomes the disadvantages with this technology.